Block copolymers having semi-crystalline blocks have been disclosed in U.S. Pat. No. 3,670,054 to De La Mare et al. De La Mare et al. disclose linear pentablock copolymers which have semi-crystalline terminal blocks comprising hydrogenated vinyl content polybutadiene. The remaining blocks of the pentablock are homopolystyrene blocks and rubbery, hydrogenated, vinyl content polybutadiene or polyisoprene blocks. The reduced terminal block size and the chemical similarity of the terminal semi-crystalline blocks and the rubber conjugated diene blocks leads to a reduced tendency for these blocks to phase separate and thereby limits the development of superior physical properties.
U.S. Pat. No. 4,107,236 to Naylor et al. discloses block copolymers having semi-crystalline blocks derived from hydrogenated polybutadiene and lacking a mono vinyl aromatic block. In particular, these hydrogenated block copolymers possessed terminal semi-crystalline, hydrogenated, vinyl butadiene blocks and interior non-crystalline, hydrogenated, rubbery vinyl butadiene blocks. The tendency for phase separation of the terminal and interior blocks was much reduced in these block copolymers thereby limiting the development of superior physical properties.
Block copolymers having semi-crystalline blocks and hydrogenated, random styrene/butadiene blocks have been disclosed in U.S. Publication No. 2008/0188580, Sasagawa et al. To demonstrate flexibility and abrasion resistance the block copolymers of Sasagawa et al. had mono vinyl aromatic comonomer in their soft blocks. In particular, mono vinyl aromatic contents of 55 to 90% were disclosed. Further, physical properties were only demonstrated after peroxide cross-linking. Therefore, any physical cross-linking due to the semi-crystalline hard blocks was insufficient for producing materials having useful physical properties.
Block copolymers having selectively hydrogenated, controlled distribution soft blocks have been disclosed in U.S. Pat. No. 7,169,848 to Bening et al. The block copolymers did not possess semi-crystalline blocks. The presence of mono vinyl aromatic blocks, particularly polystyrene blocks, provided physical cross-linking and resulted in materials useful for a wide variety of applications. In particular, these materials had novel “stretching stiffness” character. The mono vinyl aromatic blocks were susceptible to attack by solvents and in such environments dissolved or achieved inferior physical properties.
There remains a need for thermo-processable rubber materials which are strong and solvent resistant. In particular, thermally processable block copolymers are desired which are easily melt processable while able to develop strength and solvent resistance in the solid state. This combination of strength and solvent resistance will allow practical application in a wide variety of environments in which they are exposed to some level of solvent vapor or liquid. Further, such block copolymers will be useful for the preparation of compositions in which solvent resistance, high processability, and strength are needed. In addition, there remains a need for highly isotropic elastomeric films. The present disclosure addresses these needs.